Understanding The Role of Defects in WS₂ Layer in Contact with ZnO Substrate

The remarkable properties of two-dimensional (2D) materials have garnered significant attention in recent years, and understanding their fundamental behavior is critical for developing next-generation technologies. In this study, we investigate the microscopic behavior of a 2D material, WS₂, with ZnO (1 -1 0 0) taking the role as the substrate as well as charge injection layer in this van der Waals (vdW) heterostructures. Unique combination of tunable optical properties and high carrier mobility of WS₂, as well as ZnO wide band gap, large exciton binding energy and compatibility with existing fabrication technique, provides an attractive outlook for optoelectronic devices. Specifically, we aim to elucidate the role of native defects in WS₂/ZnO, such as sulphur and oxygen vacancies. Using Density Functional Theory (DFT) calculations, we examine the structural and optoelectronic properties of the WS₂/ZnO, including the impact of point defects.<br/><br/>Herein, band alignment of the heterojunction is found to be type I, with the larger band gap in ZnO, which is desirable for using ZnO as an electron injector for radiative recombination in monolayer WS₂ forming the active layer in a light-emitting device. Our results demonstrate that defects can significantly modulate the electronic properties of the interface, including band alignment and charge transfer. Furthermore, absorption and Raman spectra are calculated to understand the optical behavior of this system. These insights give crucial information for the design and optimization of devices based on 2D materials, and offer a pathway for enhancing their performance in a wide range of applications.